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SettingtheRS-485ProgrammaticallyControlledBias

ResistorswithDeviceIoControl

TheNI-Serialsoftwareusesprogrammaticcontrolcodesandthe

DeviceIoControlWindowsfunctionforprogrammingtheRS-485bias

resistormode.TosetandretrievetheRS-485biasresistormode,

completethefollowingsteps:

1. Addthefollowinglinestoyoursourcecode:

#include<winioctl.h>

#include<NiSerial.h>

NoteTheheaderfileNiSerial.hisincludedonyourNI-

SerialsoftwareCD.YoualsocanfinditintheNI-Serial

folderwhereyouinstalledyourNationalInstruments

software(typically,C:\ProgramFiles\NationalInstruments\NI-

Serial).

2. TheSERIAL_RS485_BIASattributecanhavethefollowingvalues:

RS485_BIAS_OFF

RS485_BIAS_ON

3. TosettheRS-485biasresistormode,use

NISERIAL_SET_RS485_BIASandDeviceIoControl.Forexample,

toenableprogrammaticallycontrolledRS-485biasresistors,use

thefollowingcode:

SERIAL_RS485_BIASl_SerialRs485Bias=RS485_BIAS_ON;

DWORDl_ByteCount;

DeviceIoControl(

PortHandle,

NISERIAL_SET_RS485_BIAS,

(LPVOID)&l_SerialRs485Bias,

sizeof(l_SerialRs485Bias),

(LPVOID)NULL,

0,

National Instruments PCI-8430 User Manual

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